766. Toeplitz Matrix

IsToeplitzMatrix.cs

public class Solution {
  public bool IsToeplitzMatrix(int[][] matrix) {
    var ROWS = matrix.Length;
    var COLS = matrix[0].Length;
    for(var col = 0; col < COLS; ++col)
      if(!IsEqualDiagonal(0, col, matrix))
        return false;
    
    for(var row = 0; row < ROWS; ++row)
      if(!IsEqualDiagonal(row, 0, matrix))
        return false;
    
    return true;
  }
  static bool IsEqualDiagonal(in int row, in int col, in int[][] matrix){
    var ROWS = matrix.Length;
    var COLS = matrix[0].Length;
    var cur = matrix[row][col];
    for(int dRow = row, dCol = col; dRow < ROWS && dCol < COLS; ++dRow, ++dCol){
      if(matrix[dRow][dCol] != cur)
        return false;
    }
    return true;
  }
}